Origin of Dawnside Subauroral Polarization Streams During Major Geomagnetic Storms
Origin of Dawnside Subauroral Polarization Streams During Major Geomagnetic Storms
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DOI：
10.1029/2022av000708
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发表时间：
2022-08
期刊：
影响因子：
8.4
通讯作者：
D. Lin;Wenbin Wang;V. Merkin;Chaosong Huang;M. Oppenheim;K. Sorathia;K. Pham;A. Michael;S. Bao;Qian Wu;Yongliang Zhang;M. Wiltberger;F. Toffoletto;J. Lyon;J. Garretson
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作者：
D. Lin;Wenbin Wang;V. Merkin;Chaosong Huang;M. Oppenheim;K. Sorathia;K. Pham;A. Michael;S. Bao;Qian Wu;Yongliang Zhang;M. Wiltberger;F. Toffoletto;J. Lyon;J. Garretson
太阳爆发会在近地环境中引起地磁风暴，产生肉眼可见的壮观极光，以及渗透到整个地球空间的不可见的动态变化。就在极光的赤道方向，雷达和卫星经常在黄昏到午夜的电离层中观测到强烈的向西向等离子体流，称为亚极光偏振流（SAPS）。SAPS发生在一个狭窄的纬度范围内，导致电离层等离子体和大气中性气体的强烈摩擦加热。SAPS还产生小尺度等离子体波和密度不规则性，干扰无线电通信。与通常观测到的黄昏SAPS相反，最近发现在2003年11月20日的一场超级风暴期间，在早晨部门发生了强烈的向东的极光下等离子体流。然而，这些流动的起源被称为“黎明SAPS”不能解释的相同机制，导致SAPS的黄昏，一直是一个谜。通过真实的事件全球地球空间模拟，在这里，我们证明了黎明SAPS只能发生在大风暴条件下。在这些时间内，磁层等离子体对流非常强，可以有效地将离子输送到黎明侧，而它们通常会因能量依赖性漂移而偏转到黄昏。然后，环电流压力在黎明侧积聚，并驱动连接到极光下电离层的场向电流，在那里产生向东的SAPS。在这项研究中解释的黎明SAPS的起源推进了我们对地球空间系统如何响应强烈干扰的太阳风驱动条件的理解，这些条件可能对人类社会和基础设施产生严重的不利影响。
Solar eruptions cause geomagnetic storms in the near‐Earth environment, creating spectacular aurorae visible to the human eye and invisible dynamic changes permeating all of geospace. Just equatorward of the aurora, radars and satellites often observe intense westward plasma flows called subauroral polarization streams (SAPS) in the dusk‐to‐midnight ionosphere. SAPS occur across a narrow latitudinal range and lead to intense frictional heating of the ionospheric plasma and atmospheric neutral gas. SAPS also generate small‐scale plasma waves and density irregularities that interfere with radio communications. As opposed to the commonly observed duskside SAPS, intense eastward subauroral plasma flows in the morning sector were recently discovered to have occurred during a super storm on 20 November 2003. However, the origin of these flows termed “dawnside SAPS” could not be explained by the same mechanism that causes SAPS on the duskside and has remained a mystery. Through real‐event global geospace simulations, here we demonstrate that dawnside SAPS can only occur during major storm conditions. During these times, the magnetospheric plasma convection is so strong as to effectively transport ions to the dawnside, whereas they are typically deflected to the dusk by the energy‐dependent drifts. Ring current pressure then builds up on the dawnside and drives field‐aligned currents that connect to the subauroral ionosphere, where eastward SAPS are generated. The origin of dawnside SAPS explicated in this study advances our understanding of how the geospace system responds to strongly disturbed solar wind driving conditions that can have severe detrimental impacts on human society and infrastructure.